Standard local survivability (SLS) is survivable call processing engine that provides service to the branch gateway when the branch gateway cannot reach Communication Manager. This engine is resident in the branch gateway firmware and provides basic telephony functions at the branch without being registered to Communication Manager.
The SLS features are:
Local station and outbound PSTN calling
Inbound calls over the trunks to be delivered to available stations
An H.323 gatekeeper for local IP phones to register
Call Detail Recording in a syslog format
During transition to survivability mode, only local IP-IP calls are preserved.
The link recovery process follows these steps:
While SLS is enabled and processing, the branch gateway continues to seek an alternative branch gateway controller.
If Communication Manager accepts the registration, then the active IP-to-IP calls that shuffle are preserved.
The SLS application stops processing any new calls and goes to inactive mode.
